Recent advances in multimodal imaging in tetralogy of fallot and double outlet right ventricle.

PURPOSE OF REVIEW: In the ever-evolving field of medical imaging, this review highlights significant advancements in preoperative and postoperative imaging for Tetralogy of Fallot (TOF) and double outlet right ventricle (DORV) over the past 18 months. RECENT FINDINGS: This review showcases innovations in echocardiography such as 3D speckle tracking echocardiography (3DSTE) for assessing right ventricle-pulmonary artery coupling (RVPAC) and Doppler velocity reconstruction (DoVeR) for intracardiac flow fields evaluation. Furthermore, advances in assessment of cardiovascular anatomy using computed tomography (CT) improve the integration of imaging in ablation procedures. Additionally, the inclusion of cardiac magnetic resonance (CMR) parameters as risk score predictors for morbidity, and mortality and for timing of pulmonary valve replacement (PVR) indicates its significance in clinical management. The utilization of 4D flow techniques for postoperative hemodynamic assessment promises new insights into pressure mapping. Lastly, emerging technologies such as 3D printing and 3D virtual reality are expected to improve image quality and surgical confidence in preoperative planning. SUMMARY: Developments in multimodality imaging in TOF and DORV are poised to shape the future of clinical practice in this field.

Delayed 3D IR FLASH for airway imaging in children: more than myocardial fibrosis assessment.

BACKGROUND: To investigate the ability of a delayed respiratory-navigated, electrocardiographically-gated three-dimensional inversion recovery-prepared flash low angle shot (3D IR FLASH) sequence to evaluate the lower airways in children undergoing routine cardiovascular magnetic resonance (CMR). METHODS: This retrospective study included pediatric patients (0-18 years) who underwent clinical CMR where a delayed 3D IR FLASH sequence was performed between July 2020 and April 2021. The airway image quality and extent of lower airway visibility was graded by two blinded readers using a four-point ordinal scale (0-3). Lower airway anatomical variants and abnormalities were recorded. RESULTS: 180 patients were included with a median age of 11.7 (4.6-15.3) years. 51/180 (28%) were under general anesthesia (GA). Overall, the median grading of airway image quality was 3 (2-3) and extent of lower airway visibility was 3 (3-3). Interrater agreement was almost perfect (κ = 0.867 and κ = 0.956, respectively). Image quality correlated with extent of lower airway visibility (r = 0.62, p < 0.01). Delayed 3D IR FLASH was able to characterize the segmental bronchi in 137/180 (76%) and lobar bronchi in 172/180 (96%) of patients. Lower airway abnormalities were identified in 37/180 (21%) of patients and in 33/129 (26%) with congenital heart disease (CHD). Identified abnormalities included tracheobronchial branching anomalies in 6/180 (3%), abnormal tracheobronchial situs in 6/180 (3%), and extrinsic vascular compression in 25/180 (14%). CONCLUSIONS: Delayed 3D IR FLASH has excellent performance for evaluation of the lower airway anatomy and can simultaneously assess for myocardial late gadolinium enhancement. Lower airway abnormalities are not infrequently seen in children undergoing routine CMR for CHD.

Characterization and Z-score Calculation of Cardiac MRI parameters in patients after the Fontan operation. A Fontan Outcome Registry using CMR Examinations (FORCE) study.

BACKGROUND: Cardiac magnetic resonance (CMR) offers valuable hemodynamic insights post-Fontan, but is limited by the absence of normative single ventricle data. The Fontan Outcomes Registry using CMR Examinations (FORCE) is a large international Fontan-specific CMR registry. This study used FORCE registry data to evaluate expected CMR ventricular size/function and create Fontan-specific z-scores adjusting for ventricular morphology (VM) in healthier Fontan patients. METHODS: "Healthier" Fontan patients were defined as patients free of adverse outcomes, who are New York Heart Association Class I, have mild or less valve disease, and <30% aortopulmonary collateral burden. General linear modeling was performed on 70% of the dataset to create z-scores for volumes and function. Models were tested using the remainder (30%) of the data. The z-scores were compared between children and adults. The z-scores were also compared between "healthier" Fontan and patients with adverse outcomes (death, listing for transplantation or multiorgan disease). RESULTS: The "healthier" Fontan population included 885 patients (15.0 ± 7.6 years) from 18 institutions with 1,156 CMR examinations. Patients with left ventricle morphology had lower volume, mass and higher ejection fraction (EF) compared to right or mixed (two-ventricles) morphology (p<0.001 for all pairwise comparisons). Gender, BSA and VM were used in z-scores. Of the "healthier" Fontan patients, 647 were children <18 years and 238 were adults. Adults had lower ascending aorta flow (2.9 ± 0.7 vs 3.3 ± 0.8L/min/m2, p<0.001) and ascending aorta flow z-scores (-0.16 ± 1.23 vs 0.05 ± 0.95, 0.02) compared to children. Additionally, there were 1595 patients with adverse outcomes who were older (16.1 ± 9.3 vs 15.0 ± 7.6, p<0.001) and less likely to have LV morphology (35 vs 47%, p<0.001). Patients with adverse outcomes had higher z-scores for ventricular volume and mass and lower z-scores for EF and ascending aorta flow compared to the "healthier" Fontan cohort. CONCLUSION: This is the first study to generate CMR z-scores post-Fontan. Importantly the z-scores were generated and tested in "healthier" Fontan patients and both pediatric and adult Fontan patients. These equations may improve CMR-based risk stratification after the Fontan operation.

Urgent and emergent pediatric cardiovascular imaging.

The need for urgent or emergent cardiovascular imaging in children is rare when compared to adults. Patients may present from the neonatal period up to adolescence, and may require imaging for both traumatic and non-traumatic causes. In children, coronary pathology is rarely the cause of an emergency unlike in adults where it is the main cause. Radiology, including chest radiography and computed tomography in conjunction with echocardiography, often plays the most important role in the acute management of these patients. Magnetic resonance imaging can occasionally be useful and may be suitable in more subacute cases. Radiologists' knowledge of how to manage and interpret these acute conditions including knowing which imaging technique to use is fundamental to appropriate care. In this review, we will concentrate on the most common cardiovascular emergencies in the thoracic region, including thoracic traumatic and non-traumatic emergencies and pulmonary vascular emergencies, as well as acute clinical disorders as a consequence of primary and postoperative congenital heart disease. This review will cover situations where cardiovascular imaging may be acutely needed, and not strictly emergencies only. Imaging recommendations will be discussed according to the different clinical presentations and underlying pathology.

Pseudo hepatic vein thrombosis in a newborn with infracardiac total anomalous pulmonary venous connection.

We report an interesting incidental liver finding during ECG-gated cardiac computed tomography (CT) in a newborn with infracardiac total anomalous pulmonary venous connection to the portal vein. This case shows a unique abnormality in hepatic perfusion that was initially mistaken for hepatic vein thrombosis. We review the altered hepatic blood flow distribution in this pathologic anatomy to help explain the observed hepatic perfusion abnormality on CT. This understanding will enable an imager to anticipate hepatic perfusion patterns in similar patients, potentially avoiding misdiagnosis and unnecessary further testing.

Assessment of liver fibrosis using a 3-dimensional high-resolution late gadolinium enhancement sequence in children and adolescents with Fontan circulation.

OBJECTIVES: To assess abnormal liver enhancement on 15-20 min delayed 3D high-resolution late gadolinium enhancement (3D HR LGE) sequence in patients with Fontan circulation. METHODS: Retrospective study of pediatric Fontan patients (< 18 years old) with combined cardiac-liver MRI from January 2018 to August 2021. Abnormal hepatic enhancement was graded (0-3) for each lobe, summed for a total liver enhancement score (0-6), and compared to repaired tetralogy of Fallot (rTOF) patients. Correlations with other hepatic imaging biomarkers were performed. Temporal relationships of enhancement compared to traditional early portal venous and 5-7-min delayed phase liver imaging were analyzed. RESULTS: The Fontan group (n = 35, 13 ± 3.4 years old, median time from Fontan 10 (9-12) years) had 23/35 (66%) with delayed 3D HR LGE total liver enhancement score > 0 (range 0-5), with greater involvement of the right lobe (1 (0-1) vs 0 (0-1), p < 0.01). The rTOF group (n = 35, 14 ± 2.6 years old) had no abnormal enhancement. In the Fontan group, total liver enhancement was 3 (2-4) in the early portal venous phase, lower at 1 (1-2) in the 5-7-min delayed phase (p < 0.01), and lowest at 1 (0-2) in the 15-20-min delayed phase (p = 0.03). 3D HR LGE enhancement correlated inversely with portal vein flow (rs = - 0.42, p = 0.01) and positively with left lobe stiffness (rs = 0.51, p < 0.01). The enhancement score decreased in 13/35 (37%) between the 5-7- and 15-20-min delayed phases. CONCLUSIONS: Liver fibrosis can be assessed on 3D HR LGE sequences in patients with Fontan circulation, correlates with other imaging biomarkers of Fontan liver disease, and may add information for hepatic surveillance in this population. KEY POINTS: • Abnormal liver enhancement on 3D HR LGE sequences in Fontan patients likely represents liver fibrosis and is seen in up to 66% of children and adolescents with variable distribution and severity. • The degree of 3D HR LGE liver enhancement correlates with decreased portal vein flow and increased left hepatic lobe stiffness.

Myocardial late gadolinium enhancement using delayed 3D IR-FLASH in the pediatric population: feasibility and diagnostic performance compared to single-shot PSIR-bSSFP.

BACKGROUND: This study compares three-dimensional (3D) high-resolution (HR) late gadolinium enhancement (LGE; 3D HR-LGE) imaging using a respiratory navigated, electrocardiographically-gated inversion recovery gradient echo sequence with conventional LGE imaging using a single-shot phase-sensitive inversion recovery (PSIR) balanced steady-state free precession (bSSFP; PSIR-bSSFP) sequence for routine clinical use in the pediatric population. METHODS: Pediatric patients (0-18 years) who underwent clinical cardiovascular magnetic resonance (CMR) with both 3D HR-LGE and single-shot PSIR-bSSFP LGE between January 2018 and June 2020 were included. Image quality (0-4) and detection of LGE in the left ventricle (LV) (per 17 segments), in the right ventricle (RV) (per 3 segments), as endocardial fibroelastosis (EFE), at the hinge points, and at the papillary muscles was analyzed by two blinded readers for each sequence. Ratios of the mean signal intensity of LGE to normal myocardium (LGE:Myo) and to LV blood pool (LGE:Blood) were recorded. Data is presented as median (1st-3rd quartiles). Wilcoxon signed rank test and chi-square analyses were used as appropriate. Inter-rater agreement was analyzed using weighted κ-statistics. RESULTS: 102 patients were included with median age at CMR of 8 (1-13) years-old and 44% of exams performed under general anesthesia. LGE was detected in 55% of cases. 3D HR LGE compared to single-shot PSIR-bSSFP had longer scan time [4:30 (3:35-5:34) vs 1:11 (0:47-1:32) minutes, p < 0.001], higher image quality ratings [3 (3-4) vs 2 (2-3), p < 0.001], higher LGE:Myo [23.7 (16.9-31.2) vs 5.0 (2.9-9.0), p < 0.001], detected more segments of LGE in both the LV [4 (2-8) vs 3 (1-7), p = 0.045] and RV [1 (1-1) vs 1 (0-1), p < 0.001], and also detected more cases of LGE with 13/56 (23%) of patients with LGE only detectable by 3D HR LGE (p < 0.001). 3D HR LGE specifically detected a greater proportion of RV LGE (27/27 vs 17/27, p < 0.001), EFE (11/11 vs 5/11, p = 0.004), and papillary muscle LGE (14/15 vs 4/15, p < 0.001). Inter-rater agreement for the recorded variables ranged from 0.42 to 1.00. CONCLUSIONS: 3D HR LGE achieves greater image quality and detects more LGE than conventional single-shot PSIR-bSSFP LGE imaging, and should be considered an alternative to conventional LGE sequences for routine clinical use in the pediatric population.

Imaging of pediatric cardiac tumors: A COG Diagnostic Imaging Committee/SPR Oncology Committee White Paper.

Cardiac tumors in children are rare and the majority are benign. The most common cardiac tumor in children is rhabdomyoma, usually associated with tuberous sclerosis complex. Other benign cardiac masses include fibromas, myxomas, hemangiomas, and teratomas. Primary malignant cardiac tumors are exceedingly rare, with the most common pathology being soft tissue sarcomas. This paper provides consensus-based imaging recommendations for the evaluation of patients with cardiac tumors at diagnosis and follow-up, including during and after therapy.

Cardiac Magnetic Resonance Imaging to Determine Single Ventricle Function in a Pediatric Population is Feasible in a Large Trial Setting: Experience from the Single Ventricle Reconstruction Trial Longitudinal Follow up.

The Single Ventricle Reconstruction (SVR) Trial was a randomized prospective trial designed to determine survival advantage of the modified Blalock-Taussig-Thomas shunt (BTTS) vs the right ventricle to pulmonary artery conduit (RVPAS) for patients with hypoplastic left heart syndrome. The primary aim of the long-term follow-up (SVRIII) was to determine the impact of shunt type on RV function. In this work, we describe the use of CMR in a large cohort follow up from the SVR Trial as a focused study of single ventricle function. The SVRIII protocol included short axis steady-state free precession imaging to assess single ventricle systolic function and flow quantification. There were 313 eligible SVRIII participants and 237 enrolled, ages ranging from 10 to 12.5 years. 177/237 (75%) participants underwent CMR. The most common reasons for not undergoing CMR exam were requirement for anesthesia (n = 14) or ICD/pacemaker (n = 11). A total of 168/177 (94%) CMR studies were diagnostic for RVEF. Median exam time was 54 [IQR 40-74] minutes, cine function exam time 20 [IQR 14-27] minutes, and flow quantification time 18 [IQR 12-25] minutes. There were 69/177 (39%) studies noted to have intra-thoracic artifacts, most common being susceptibility artifact from intra-thoracic metal. Not all artifacts resulted in non-diagnostic exams. These data describe the use and limitations of CMR for the assessment of cardiac function in a prospective trial setting in a grade-school-aged pediatric population with congenital heart disease. Many of the limitations are expected to decrease with the continued advancement of CMR technology.

Hemodynamic effects of pulmonary regurgitation in one and one-half ventricle repair.

The pulmonary circulation after one and one-half ventricle repair is complex because of the direct connection of two sources of blood flow. Associated pulmonary regurgitation further complicates the pulmonary circulation. We report the complex hemodynamics depicted by phase-contrast magnetic resonance imaging in a patient with one and one-half ventricle circuit and severe pulmonary regurgitation. Antegrade superior vena caval flow occurred almost exclusively during diastole and regurgitated into the right ventricle. Consequently, the entire systemic venous return reached the right ventricle during diastole and is pumped back into the pulmonary arteries in systole. The case highlights the importance of analyzing flow patterns phase-by phase throughout the cardiac cycle instead of relying on the net flow volumes through each source of pulmonary blood flow.

Contrast-enhanced body magnetic resonance angiography: how we do it.

This review introduces the basic principles of contrast-enhanced magnetic resonance (MR) angiography and details four contrast-enhanced MR angiography sequences for body imaging with extracellular gadolinium-based contrast agents in pediatric patients. Specifically, this review covers (1) respiratory-navigated, cardiac-gated MR angiography; (2) time-resolved MR angiography; (3) conventional MR angiography; and (4) modified spoiled gradient echo variants. We present and discuss indications, technical considerations, sequence optimization, advantages and disadvantages, along with practical tips and illustrative case examples for each sequence.

Semiquantitative characterization of dynamic magnetic resonance perfusion of the liver in pediatric Fontan patients.

BACKGROUND: Dynamic contrast-enhanced magnetic resonance imaging (MRI) of the liver in pediatric Fontan patients often shows peripheral reticular areas of hypoenhancement, which has not been studied in detail. OBJECTIVE: To semiquantitatively score the hepatic MR perfusion abnormality seen in pediatric Fontan patients, and to correlate the perfusion abnormality with functional clinical and hemodynamic parameters. MATERIALS AND METHODS: All children (< 18 years old) after Fontan palliation with combined clinical cardiac and liver MRI performed between May 2017 and April 2019 were considered for inclusion. A semiquantitative perfusion score was used to assess the severity of the hepatic reticular pattern seen on dynamic contrast-enhanced liver imaging. The liver was divided into four sections: right posterior, right anterior, left medial and left lateral. Each liver section was assigned a score from 0 to 4 depending on the amount of abnormal reticular hypoenhancement. Scoring was assigned for each section of the liver across eight successive dynamic contrast-enhanced modified spoiled gradient echo runs. Scores were correlated with clinical and hemodynamic parameters. RESULTS: All Fontan children showed hepatic reticular hypoenhancement by MRI, most severe in the early portal venous phase with a median maximum total perfusion abnormality score of 12 (range: 9-14). All perfusion abnormalities progressively resolved during the hepatic venous phase. Perfusion abnormality scores were greatest in the right compared to left hepatic lobes (7 range: [6-8] vs. 5 [range: 3-6], P < 0.01). The maximum left hepatic lobe perfusion abnormality scores were greatest in children with versus without imaging signs of portal hypertension (8 [range: 7-8] vs. 4 [range: 3-5], P < 0.01). High unconjugated bilirubin and low platelets correlated with greater perfusion abnormality (R = 0.450, P = 0.024, and R = - 0.458, P < 0.01, respectively). Age at MRI, time from Fontan, focal liver lesions and cardiac MRI hemodynamic parameters did not show significant correlations with the severity of the liver perfusion abnormality. CONCLUSION: All Fontan children have hepatic reticular hypoenhancement abnormalities seen with MRI that are most severe in the right hepatic lobe and universally show gradual resolution through the hepatic venous phase. Perfusion abnormality in the left hepatic lobe is worse in children with portal hypertension.

Abdominal lymphatic system visibility, morphology, and abnormalities in children as seen on routine MCRP and its association with immune-mediated diseases.

PURPOSE: (1) To assess the visibility and diameters of the thoracic duct (TD) and cisterna chyli (CC) on MR cholangiopancreatography (MRCP) in children. (2) To evaluate for the presence of any lymphatic abnormalities and assess their association with diseases in which the immune system is implicated in etiopathogenesis. METHODS: This retrospective study included 142 MRCPs performed in children 8-17 years old and without prior surgeries. Two radiologists reviewed all exams for visibility and diameters of the TD and CC, and presence of abnormal lymphatic collaterals. TD and CC diameters in various disease processes were compared using Student's t tests. The association of collaterals with immune-mediated diseases was assessed using Fisher's exact tests. RESULTS: The TD and CC were seen in 134/142 (93.7%) cases with mean diameter of 3.25 ± 1.07 mm and 126/142 (88.7%) cases with mean diameter of 4.55 ± 1.37 mm respectively. The mean diameter of CC was larger in patients with portal hypertension (p = 0.021). There were no significant differences in the TD and CC diameters between immune-mediated and non-immune-mediated diseases. Retroperitoneal collaterals were seen in 41/142 (28.8%) of cases and were associated with both portal hypertension (p = 0.0019) and immune-mediated diseases (p = 0.0083). CONCLUSION: The TD and CC can be visualized in the majority of children on routine MRCP images, and CC has larger diameter in patients with portal hypertension. The association of collaterals with immune-mediated diseases supports a potential role of the lymphatic system in the etiopathogenesis of immune-mediated diseases. KEY POINTS: • The lymphatic system has been increasingly implicated in a number of inflammatory and immune-mediated diseases. • The abdominal lymphatic system can be visualized in the majority of children above 8 years on routine MRCP images. Similar to adult studies, the cisterna chyli is significantly larger in children with portal hypertension. • Retroperitoneal lymphatic collaterals, seen in 29% children, are associated with immune-mediated diseases, which supports the potential role of the lymphatic system in the pathogenesis of immune-mediated diseases.

Adverse fibrosis remodeling and aortopulmonary collateral flow are associated with poor Fontan outcomes.

BACKGROUND: The extent and significance in of cardiac remodeling in Fontan patients are unclear and were the subject of this study. METHODS: This retrospective cohort study compared cardiovascular magnetic resonance (CMR) imaging markers of cardiac function, myocardial fibrosis, and hemodynamics in young Fontan patients to controls. RESULTS: Fifty-five Fontan patients and 44 healthy controls were included (median age 14 years (range 7-17 years) vs 13 years (range 4-14 years), p = 0.057). Fontan patients had a higher indexed end-diastolic ventricular volume (EDVI 129 ml/m2 vs 93 ml/m2, p < 0.001), and lower ejection fraction (EF 45% vs 58%, p < 0.001), circumferential (CS - 23.5% vs - 30.8%, p < 0.001), radial (6.4% vs 8.2%, p < 0.001), and longitudinal strain (- 13.3% vs - 24.8%, p < 0.001). Compared to healthy controls, Fontan patients had higher extracellular volume fraction (ECV) (26.3% vs 20.6%, p < 0.001) and native T1 (1041 ms vs 986 ms, p < 0.001). Patients with a dominant right ventricle demonstrated larger ventricles (EDVI 146 ml/m2 vs 120 ml/m2, p = 0.03), lower EF (41% vs 47%, p = 0.008), worse CS (- 20.1% vs - 25.6%, p = 0.003), and a trend towards higher ECV (28.3% versus 24.1%, p = 0.09). Worse EF and CS correlated with longer cumulative bypass (R = - 0.36, p = 0.003 and R = 0.46, p < 0.001), cross-clamp (R = - 0.41, p = 0.001 and R = 0.40, p = 0.003) and circulatory arrest times (R = - 0.42, p < 0.001 and R = 0.27, p = 0.03). T1 correlated with aortopulmonary collateral (APC) flow (R = 0.36, p = 0.009) which, in the linear regression model, was independent of ventricular morphology (p = 0.9) and EDVI (p = 0.2). The composite outcome (cardiac readmission, cardiac reintervention, Fontan failure or any clinically significant arrhythmia) was associated with increased native T1 (1063 ms vs 1026 ms, p = 0.029) and EDVI (146 ml/m2 vs 118 ml/m2, p = 0.013), as well as decreased EF (42% vs 46%, p = 0.045) and worse CS (- 22% vs - 25%, p = 0.029). APC flow (HR 5.5 CI 1.9-16.2, p = 0.002) was independently associated with the composite outcome, independent of ventricular morphology (HR 0.71 CI 0.30-1.69 p = 0.44) and T1 (HR1.006 CI 1.0-1.13, p = 0.07). CONCLUSIONS: Pediatric Fontan patients have ventricular dysfunction, altered myocardial mechanics and increased fibrotic remodeling. Cumulative exposure to cardiopulmonary bypass and increased aortopulmonary collateral flow are associated with myocardial dysfunction and fibrosis. Cardiac dysfunction, fibrosis, and collateral flow are associated with adverse outcomes.

Usefulness of TI-scout images in the assessment of late gadolinium enhancement in children.

BACKGROUND: Cardiovascular magnetic resonance (CMR) late gadolinium enhancement (LGE) requires identification of the normal myocardial nulling time using inversion time (TI)-scout imaging sequence. Although TI-scout images are not primarily used for myocardial assessment, they provide information regarding different signal recovery patterns of normal and abnormal myocardium facilitating identification of LGE in instances where standard LGE images alone are not diagnostic. We aimed to assess the diagnostic performance of TI-scout as compared to that of standard LGE images. METHODS: CMR studies with LGE imaging in 519 patients (345 males, 1-17 years) were reviewed to assess the diagnostic performance of LGE imaging in terms of the location of LGE and the pathologic entities. The diagnostic performance of the TI-scout and standard LGE imaging was classified into four categories: (1) equally diagnostic, (2) TI-scout superior to standard LGE, (3) standard LGE superior to TI-scout, and (4) complementary, by the consensus of the two observers. RESULTS: The study cohort consisted of 440 patients with negative LGE and 79 with evidence for LGE. For a negative diagnosis of LGE, TI-scout and standard LGE images were equally diagnostic in 75% of the cases and were complementary in 12%. For patients with LGE, TI-scout images were superior to standard LGE images in 52% of the cases and were complementary in 19%. The diagnostic performance of TI-scout images was superior to that of standard LGE images in all locations. TI-scout images were superior to standard LGE images in 11 of 12 (92%) cases with LGE involving the papillary muscles, in 7 /12 (58%) cases with subendocardial LGE, and in 4/7 (57%) cases with transmural LGE. TI-scout images were particularly useful assessing the presence and extent of LGE in hypertrophic cardiomyopathy (HCM). TI-scout was superior to standard LGE in 6/10 (60%) and was complementary in 3/10 (30%) of the positive cases with HCM. CONCLUSIONS: TI-scout images enhance the diagnostic performance of LGE imaging in children.

Abdominal Imaging of Children and Young Adults With Fontan Circulation: Pathophysiology and Surveillance.

OBJECTIVE. The Fontan procedure has significantly improved the survival in children with a functional single ventricle, but it is associated with chronically elevated systemic venous pressure that leads to multisystemic complications. Imaging plays an important role in assessing these complications and guiding management. The pathophysiology, imaging modalities, and current surveillance recommendations are discussed and illustrated. CONCLUSION. Significant improvement in survival of patients with Fontan circulation is associated with ongoing cardiac and extracardiac comorbidities and multisystemic complications. The liver and intestines are particularly vulnerable to damage. In addition, this patient population has been shown to be at increased risk of certain malignancies such as hepatocellular carcinoma and neuroendocrine tumors. Familiarity with imaging findings of Fontan-associated liver disease and other abdominal complications of the Fontan circulation is essential for radiologists because we are likely to encounter these patients in our general practice.

Increased extracellular volume in the liver of pediatric Fontan patients.

BACKGROUND: Patients with single ventricle physiology are at increased risk for developing liver fibrosis. Its extent and prevalence in children with bidirectional cavopulmonary connection (BCPC) and Fontan circulation are unclear. Extracellular volume fraction (ECV), derived from cardiovascular magnetic resonance (CMR) and T1 relaxometry, reflect fibrotic remodeling and/or congestion in the liver. The aim of this study was to investigate whether pediatric patients with single ventricle physiology experience increased native T1 and ECV as markers of liver fibrosis/congestion. METHODS: Hepatic native T1 times and ECV, using a cardiac short axis modified Look-Locker inversion recovery sequence displaying the liver, were measured retrospectively in children with BCPC- and Fontan circulations and compared to pediatric controls. RESULTS: Hepatic native T1 time were increased in Fontan patients (n = 62, 11.4 ± 4.4 years, T1 762 ± 64 ms) versus BCPC patients (n = 20, 2.8 ± 0.9 years, T1 645 ± 43 ms, p = 0.04). Both cohorts had higher T1 than controls (n = 44, 13.7 ± 2.9 years, T1 604 ± 54 ms, p < 0.001 for both). ECV was 41.4 ± 4.8% in Fontan and 36.4 ± 4.8% in BCPC patients, respectively (p = 0.02). In Fontan patients, T1 values correlated with exposure to cardiopulmonary bypass time (R = 0.3, p = 0.02), systolic and end diastolic volumes (R = 0.3, p = 0.04 for both) and inversely with oxygen saturations and body surface area (R = -0.3, p = 0.04 for both). There were no demonstrable associations of T1 or ECV with central venous pressure or age after Fontan. CONCLUSION: Fontan and BCPC patients have elevated CMR markers suggestive of hepatic fibrosis and/or congestion, even at a young age. The tissue changes do not appear to be related to central venous pressures. TRIAL REGISTRATION: Retrospectively registered data.

Mapping versus source methods for quantifying myocardial T1 in controls and in repaired tetralogy of Fallot: interchangeability and reproducibility in children.

BACKGROUND: Myocardial T1 relaxometry can be performed by contouring on individual T1-weighted source images (source method) or on a single T1 map (mapping method). OBJECTIVE: This study compares (a) agreement between native T1 and extracellular volume results of the two methods and (b) interobserver reproducibility of the two methods in children without heart disease and those with tetralogy of Fallot (TOF). MATERIALS AND METHODS: We retrospectively analyzed pediatric patients (controls and those with repaired TOF) with cardiac magnetic resonance examinations including extracellular volume quantification using the modified Look-Locker inversion recovery (MOLLI) sequence. We compared native T1 and extracellular volume of the entire left ventricle and interventricular septum derived using the source and the mapping approaches. RESULTS: In the control group (n=25, median age 14.0 years, interquartile range [IQR] 11.5-16.5 years), the mapping method produced lower native T1 values than the source method in the interventricular septum (mean difference ± standard deviation [SD] = 12±15 ms, P<0.001). In the TOF group (n=50, median age 13.3 years, IQR 9.9-15.0 years), the mapping method produced lower values for native T1 and extracellular volume in the interventricular septum (mean difference 9±14 ms and 0.6±1.1%, P<0.001). In 6-12% of the children, differences were >3 standard deviations from the mean difference. Interobserver reproducibility between the two methods by intraclass correlation coefficients were clinically equivalent. CONCLUSION: T1 and extracellular volume values generated by the source and mapping methods show systematic differences and can vary significantly in an individual child, and thus cannot be used interchangeably in clinical practice. The source method might allow for easier detection and, in some cases, mitigation of artifacts that are not infrequent in children and can be difficult to appreciate on the T1 map.

Dual phase infusion with bolus tracking: technical innovation for cardiac and respiratory navigated magnetic resonance angiography using extracellular contrast.

This technical innovation paper describes a technique for performing cardiac-gated, respiratory-navigated cardiovascular magnetic resonance angiography using an extracellular gadolinium-based contrast agent at 1.5 Tesla (T) with a dual phase bolus injection and slow infusion technique.